Organoclays prepared from montmorillonites with tetramethylolphosphonium chloride in different pH conditions

Alkylammonium montmorillonite (MMT) has onset temperature of degradation in the same temperature range used for compounding thermoplastics, thus, requiring more thermally stable organic cations. In the current study, phosphonium ions were exchanged in the interlayer of MMT. Na-MMT was modified with quaternary phosphonium salts, tetramethylolphosphonium chloride (THPC), via ion-exchange reactions, in different pH value conditions. The interlayer space, interlamellar structure, thermal stability, and surface morphology of these organic montmorillonites (THPC-OMMTs) were investigated by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM)-energy dispersing spectrometer (EDS) as well as transmission electron microscopy (TEM). FTIR analysis revealed that the organic modification was successfully achieved due to the bands at 3626 and 3421 cm− 1 referring to OH stretching region in THPC. TGA results indicated that the thermal stability of these THPC-OMMTs was obviously improved compared with that of MMT with different degradation modes. XRD analysis clarified that the interlayer spacing of Na-MMT was changed from 1.43 to 1.26–1.58 nm in the organoclays prepared in different pH values. The SEM-EDS results provided the evidence that THPC was intercalated throughout the interlayer spaces or adsorbed onto the clay surface in different conditions. TEM micrographs demonstrated a partially intercalated and aggregated morphology together with the increased silicate gallery spacing. In conclusions, in the acid conditions, THPC was more stable and conducive for intercalation, and the interlayer spacing of montmorillonite had been expanded and possessed good thermal stabilities due to steric hindering and thermal stability of the surfactant.